Limited overlap between the seismic gap and coseismic slip of the great 2010 Chile earthquake

Journal name:
Nature Geoscience
Volume:
4,
Pages:
173–177
Year published:
DOI:
doi:10.1038/ngeo1073
Received
Accepted
Published online
Corrected online

The Mw 8.8 mega-thrust earthquake and tsunami that occurred on 27 February 2010 offshore the Maule region, Chile, was not unexpected. A clearly identified seismic gap1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 existed in an area where tectonic loading has been accumulating since the great 1835 earthquake14. Here we jointly invert tsunami and geodetic data to derive a robust model for the coseismic slip distribution and induced coseismic stress changes. We compare these with past earthquakes and the preseismic locking distribution13, to assess if the Maule earthquake has filled the seismic gap. We find that the main slip patch is located to the north of the gap, overlapping the rupture zone of the Mw 8.0 earthquake that occurred in 1928, with a secondary concentration of slip to the south. The seismic gap was only partially filled and a zone of high preseismic locking remains unbroken, inconsistent with the assumption that distributions of seismic rupture might be correlated with preseismic locking. Moreover, we conclude that increased stress on the unbroken patch may in turn have increased the probability of another major to great earthquake there in the near future.

At a glance

Figures

  1. Location map of the 2010 Maule earthquake and the seismic gap.
    Figure 1: Location map of the 2010 Maule earthquake and the seismic gap.

    Geographic location of the 27 February 2010 Mw 8.8Maule earthquake, with epicentre (red star) between Concepción and Constitución in South Central Chile. The green and white ‘beach ball’ is the United States Geological Survey centroid moment tensor. Yellow stars are the epicentres of 1928, 1939, 1960 and 1985 earthquakes, with their approximate source zones4, 7, 16, 19, which are shaded for thrust inter-plate events. The 1960 source zone includes both 21 May Mw 7.9 and 22 May Mw 9.5 earthquakes19. Orange lines are contours of the preseismic locking distribution13. The segment that probably contains the source zone of the 1835 earthquake (indicated by the black dashed line with arrows) is the zone of the Darwin14 gap, where a major earthquake was expected12. The red line with triangles is the trench between the Nazca and South America Plates26. The white arrow indicates the approximate convergence direction of the plates along with its estimated velocity10.

  2. Slip distribution of the 2010 Maule earthquake.
    Figure 2: Slip distribution of the 2010 Maule earthquake.

    Slip distribution for the 2010 Mw8.8 Maule earthquake obtained from the joint inversion of tsunami and geodetic data, represented by colours according to the scale at the bottom. White arrows represent the slip direction (rake). Thin black contours indicate the associated surface vertical displacement (1-m-interval solid lines for uplift, 20-cm-interval dashed lines for subsidence). Epicentres and source zones are plotted only for major thrust earthquakes (compare Fig. 1).

  3. Comparison between observed and predicted data sets.
    Figure 3: Comparison between observed and predicted data sets.

    a, Observed and predicted tsunami time series. Peak value (m) is indicated for each station. Abbreviated station names are as in Supplementary Table S2. b, Observed and predicted GPS vectors. Contour lines of predicted vertical displacement as in Fig. 2. Yellow squares indicate positions of land-level-change measurements. c, Observed and predicted land-level changes. Error bars for observed data are experimental uncertainties15, whereas for predicted data they are calculated adding ±1σ errors (Supplementary Table S1) to the average slip model. d, Residuals between observed and predicted InSAR LOS displacement expressed as percentages of the observed data values.

  4. Comparison of the Maule earthquake slip distribution and coseismic stress variation to preseismic locking and past earthquakes.
    Figure 4: Comparison of the Maule earthquake slip distribution and coseismic stress variation to preseismic locking and past earthquakes.

    a, Slip distribution for the Maule earthquake compared with the estimated position of the Darwin gap, in the segment where the 1835 earthquake probably occurred. Source zones of past thrust earthquakes as in Fig. 1. White lines are preseismic locking contours as in Fig. 1. The Darwin gap was only partially filled and a zone of high preseismic locking remains unbroken. b, Coulomb stress changes associated with the Maule earthquake, resolved on the mega-thrust surface. Positive stress changes may favour a future rupture. An increase of stress occurring after the Maule earthquake in the Darwin gap might have increased the probability of a future earthquake there.

Change history

Corrected online 08 February 2011
In the version of this Letter originally published online, the y-axis values and label were missing from Fig. 3c. This error has now been corrected in all versions of the Letter.

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Affiliations

  1. Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy

    • S. Lorito,
    • F. Romano,
    • S. Atzori,
    • A. Avallone,
    • M. Cocco,
    • E. Boschi &
    • A. Piatanesi
  2. Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0225, USA

    • X. Tong
  3. Environmental Sciences Research Institute, School of Environmental Sciences, University of Ulster, Coleraine BT52 1SA, Northern Ireland

    • J. McCloskey

Contributions

S.L., F.R. and A.P. were involved in all of the phases of this study. S.A., X.T. and A.A. processed, modelled and analysed geodetic data, and wrote part of the Methods. J.M. and M.C. contributed to result interpretation and paper writing. E.B. promoted the experiment, contributed to result interpretation and supported the project.

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The authors declare no competing financial interests.

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